This invention relates to combustion liners for turbine types of power plants and particularly to the manifolding of cooling air around the combustion and dilution air holes in a Finwall constructed liner.
This invention constitutes an improvement over the cool air manifold means described and claimed in U.S. Pat. No. 3,545,202 granted to Batt et al on Dec. 8, 1970 and assigned to the same assignee as this application and being incorporated herein by reference.
As shown in U.S. Pat. No. 3,545,202, supra, the grommet surrounding the air hole admitting air internally of the combustor is designed for a liner fabricated from Finwall.RTM. constructed panels, which panels are shown therein. As noted from reading this patent, the flow around the grommet is conducted through a header that maintains a continuous flow path in the Finwall channels from upstream to downstream of the grommet. Hence, the air in the Finwall channels immediately upstream of the grommet since it is in direct heat exchange relation with the hot combustion products is at a higher temperature than the cooling air, and conducting it downstream of the grommet has been found, owing to this quantity of heat, to deteriorate the life of the combustor liner at this point. This is illustrated in FIG. 1 showing the prior art where the Finwall constructed panel is drilled to admit combustion air at aperture 10. Grommet 12 surrounds the aperture and is rolled over at the top surface adjacent the cooling air side to form manifold 14. The adjacent fins under the manifold are cut away at 15 so that air flowing in the immediate Finwall channels flows around the grommet from upstream to downstream and flows the full length of the panel, impairing the cooling capabilities of this cooling air. It will also be noted that in actual practice the grommet is secured in place by the 360.degree. weldment 16 to the plate of the Finwall liner exposed to the combustion gases, which has proven to limit the life of this type of construction.
We have found that we can obviate the problems noted above by providing a reentry of fresh cooling air to cool the Finwall passages on the downstream side of the grommet or the combustion or dilution air holes fabricated according to this invention or in installation not using the grommet. Thus, the air adjacent the grommet or combustion and dilution air holes on the upstream end is diverted to discharge into the combustor at the junction points. Additionally, this invention contemplates the elimination of the weldment in its entirety or the relocation thereof to enhance the life of the liner. In a design which requires welding the cold grommet to the hot inner plate it is fundamental that the thermal differences serve to create shear forces in the weld leading to weld cracking. The preferred embodiment requires only a partial weld hence provides for a redistribution and a reduction in stresses, improving weld crack resistance. In another embodiment the elimination of the weld eliminates this failure mode entirely, and obviously, this would be the case when a grommet is not used.